What Causes Compressor Leads to Burn Off of Terminals?

[Ken Hall]

For the 12 years we've had this condenser unit the compressor leads have burned off at the terminals once or twice a year. These events burn the insulation off the wires back about 3 inches from the connection, and seem to char the wire itself to the same point but it may just be the burned insulation making it look like the wires were burned.

For the 10 years my unit was under warranty I simply called the people who installed it, they'd come out, cut off the burned wire ends add some inadequate crimped on connectors and it would work for 6-12 more months. Now that the warranty has run out this has become my job. This summer it's begun doing this more frequently and the events seem to be getting closer and closer together. I'm pretty sure this even happen upon startup because I've heard the breakers snap a couple of times shortly after the indoor fan comes on, and when I go out and look the leads are burned.

Based on advice I got here I installed a set of Term-Loc leads about 6 weeks ago. A week ago these leads burned (just like the old ones). The connectors stayed on but one lead burned completely off its Term-Loc connector. The event melted/burned up the plastic terminal separator that comes in the Term-Loc kit. I wasn't able to attach the burned off lead to the Term-Loc connector again, so I went back to my old method that used to last 6 months to a year. Night before last the same lead burned off again.

My question is, what causes compressor leads to burn off of terminals repeatedly like this? Remember it has been happening fairly regularly for 12 years so it isn't a condition caused by age.

This unit has a black cylindrical thing connected to the run capacitor. It has the name Supco Super-Boost. [See picture

It has words on it that sound like it's a compressor start booster. Suggesting it gives the compressor a big current hit on startup to kick the motor into motion. Could this be causing the wires to burn? If so, why do I need it and can I remove it? If I can remove it, do I just disconnect it from the start capacitor?

-- Ken

[Al Moran]

Your thermostat is causing "high voltage crossover" at the contactor where the two wires come into the condenser from the indoor circuit board. Replace the thermostat and all will be well. Such a simple fix, you must of had an idiot working on it.

[DIMwit]

I see a pattern here: you are the anti-stormy.

Stormy tried to fit it by being nice and offering poor help. you try to fit in by being a prick and offering Bubba-ish help.

Bubba wins, but you are his protégé, I guess? Bubba at least seems to know what he talks about. You are years away from that. If you think his compressor is bad, why don't you mention that?

Dimwit (at least I admit it) sprinkler system armed

[udarrell]

The initial problem may have happened because the connections were not tight enough. That causes resistance that generates a lot of heat that turns the terminal on the compressor into resistive poor conductors therefore the scenario keeps repeating.

They need to take some emery paper and tire to get down to a better conduction surface. Also, is the compressor running too hot?

If the compressor terminals appear to be too burnt & emery or filing does not help along with special screw tight terminal clamps, then eventually it will get to hot & blow a hole in the terminal plug, resulting in the loss of all the refrigerant. - udarrell

[Al Moran]

Yawn.

[Stormin Mormon]

That was a terrific photo of the boost kit in the connection box. I wonder if the gentleman with the unit would be kind enough to post anohter pic, this one of the terminals.

That's something I'd not thought of, bad connection inside the compressor. Of course, where the terminal block ataches to the internal wiring may be high resistance.

And my favorite reccomendation -- clean the condensor.

[Ken Hall]

When I installed the Term-Loc connectors I used sandpaper to try to clean the terminals, but they're pretty burnt after all these incidents. I considered filing them but the location is too awkward for that.

I don't know how to judge too hot. I can put my hand on it be I can't leave it there.

That's what the Term-Loc connectors are. They have a set screw that screws down onto the terminals.

-- Ken

[Oscar_Lives]

Sounds like a bad or improper thermostat is being used. What make/model thermostat do you have?

[AKS]

Ken Udarrell have gave you good explanation I had few of those myself but so far none repeated, these is what I do when you replacing terminal (stay-cons) first make sure you wires are rated for current require, crimping wire some time it is not enough you may need to solder in and then make sure that terminal fits on tight you can also squeeze in terminal part that goes on to log before it is pushed on, after that is complete you can add small glob of silicon compound on to each terminal preventing getting moisture on and helping keep rust off. Good luck from Dido

[Ken Hall]

That's baffling to me. How can a thermostat cause this? As far as I know all the thermostat does is supply 24v to energize the contactor when cooling is called for.

My thermostat is a Honeywell Chronotherm III.

Incidentally if you're thinking the contactor is chattering when energized, it's not. There's just one solid clack.

-- Ken

[Power's Mechanical]

Dont mind Oscar. He's one of many HVAC groupies here that dont have one thing to do with HVAC besides sit at the computer and post non stop bullshit to a HVAC newsgroup.

[Jabs]

Ken, The answer to your problem at:

Jabs

[Noon-Air]

Damn... how can they sell them so cheap? LOL

[Bubba]

So you mean I won a prize? Just forward the money to my PayPal acct. Bubba

[Bubba]

We know its baffling to you. That's why you're here. Trust us. We know what we are talking about. Now go get a new thermostat. You might want to also install one of those new ReverseFlow@ductboosters while you're at it.

Clack? Oh shit! Never mind. You need to replace your system immediately. Bubba

[Mo Hoaner]

He was actually giving away a possible cause of the problem. What sometimes happens is that the stat starts the compressor - that's the "one solid clack" you hear. Now, the system comes up to normal operating pressure. The thermostat might have a problem (it might not even be the stat's fault - think door slamming near a mercury stat) where it momentarily allows the contactor for the compressor to open. Now it closes the contactor again. We've got head pressure, so you wind up with a locked rotor condition. If the compressor is running, it draws - oh... something less than the rating of the breaker feeding it. During a start, and while you are in a locked rotor condition, it sits there drawing whatever it feels like - some large multiple of the recommended breaker rating until something gives. That would be one of the thermals, the breaker feeding it, or the wiring to it, or the windings. Something is wrong with this picture. It could very well be the thermostat. The real expensive, good ones are recommended for a good reason - they generally have a parameter that allows the knowledgable installer to control the minimum cycle time.

From what you've said, it's been happening every six months for the past 12 years. That means - to me, anyway - that six months after you had this unit installed, it burned it's first set of leads off. After the second time it happened - and certainly during the 7th, 8th, or 9th year it happened - you should have been asking a few questions about why it keeps happening, and what they plan on doing when the manufacturer's / installer's warranty is over. The wire to that you are trying so hard to re-attach is so badly corroded, and contaminated with Hydrochloric acid from the burned PVC that there is no hope of a permanent repair with the present wire. You need to find someone who knows what they are doing to look at the unit, and assess whether the terminals are too far gone, whether there's an issue with the control system, and whether it's just time to say goodbye to it. That would likely be someone other than who's been out there between 12 and 24 times for the "same" problem.

Somewhere along the line, did they at least suggest replacing the compressor, and you didn't want to pay the labor? When you are messing with those terminals, are you using correct PPE? Remember that there's 50-100 PSI - when it has been off for a while - behind those innocent looking little studs. The glass seals have likely been stressed by the heat, and a nice R-22 / oil injection into your hand might be the most minor thing that could happen. BTW, you could lose fingers / hand later due to gangrene if it lets go, and the conditions are right.

[Noon-Air]

IF the super boost was correctly installed, it *might* help, so would correctly wiring that replacement run capacitor(it *IS* the correct value, isn't it?)...however, the contactor looks like it has been arced across and it should probably be replaced and the original problem corrected. Unless I miss my guess, its a Goodman unit that has been repeatedly hacked over by the lowest bidder and then screwed with by the owner.

Its pointless to ask what kind of metering device does the system have?? When the compressor *IS* running, what is the SST and superheat?? What is the LLP and subcooling?? What is the amp draw on the compressor??

Best you can hope for is to call a *competent*(not cheapest), licensed, insured, professionally trained, HVAC technician to come straighten out your mess.

[DIMwit]

the prize committee budget is poorly funded; best we can do is send you a slightly used 5 cent cigar that was used by some porno queen showing off one of her many talents. Just saved up enough bottles and cans to get enough cash to fine dine at Burger King.

I love this group. ( hey!, but only in a plutonic way).

snipped for; cause I want to

[DIMwit]

Is your name spelled correctly at the end?

[Ken Hall]

It's a Copeland compressor in an Amana condenser unit.

The "hacking" I've done is: changed the contactor once installing inadequate connectors (same as the original installer used) when they burned off shortly thereafter installing the Term-Loc wires -- at your suggestion if I recall correctly installing the inadequate connectors twice more in the last couple of weeks after the Term-Loc wire burned off.

The last two events prompting me to post this question.

This depends on the conditions. The last time I made measurements these were the conditions and results:

indoor temp 74 outdoor temp 95 low side pressure 67 saturation temp 38 suction line temp 45 superheat 7 superheat should be 7 per manufacture's pamphlet

18 amps -- about right for the conditions per manufacturer's pamphlet

-- Ken